The invention discloses a test system and method for a performance of an electronic current transformer. The system is composed of a standard current transformer, a testing electronic current transformer, a sampling rate adaptive module, and a merging unit, wherein primary sides of the standard current transformer and the testing electronic current transformer are connected in series. The input terminal of the sampling rate adaptive module is connected with the output terminal of the testing electronic current transformer; the input terminal of the merging unit module is connected with the output terminals of the standard current transformer and the sampling rate adaptive module respectively. According to the invention, with simultaneous access of electromagnetic current transformer and the testing electronic current transformer sampling loops in hybrid sampling differential protection, time delay testing of a hybrid sampling differential loop is completed by using the electromagnetic current transformer as a reference. The system and method are applied to delay compensation in UPFC protection.